Assertion (A): Nighttime temperatures in the central parts of the city are generally higher than those over the surrounding rural areas

Reason (R): Radiation losses over the urban areas are less than those over the rural areas

Choose the correct option:

The climatic conditions of an urban area differ from the climate of rural surroundings. As urban areas develop, changes occur in their landscape.

• Buildings, roads, and other infrastructure replace open land and vegetation. Surfaces that were once permeable and moist become impermeable and dry.
• These changes cause urban regions to become warmer than their rural surroundings, forming an "island" of higher temperatures in the landscape.
• An urban heat island (UHI), is a metropolitan area that's a lot warmer than the rural areas surrounding it.

• The temperature difference is usually larger at night than during the day and larger in winter than in summer. At night, radiative losses from urban building and street materials keep the city’s air warmer than that of rural areas.
• The primary cause includes a city’s weather conditions, urbanization and waste heat generated by energy use.    
• When houses, shops, and industrial buildings are constructed close together, it can create a UHI. Building materials are usually very good holding in heat. This makes the areas around buildings warmer.
• Waste heat also contributes to UHI. People and their tools, such as cars and factories, are always burning off energy, this energy usually escapes in the form of heat. And if there are a lot of people in one area, that's a lot of heat.

Hence, it is obvious from the given points that Both (A) and (R) are true and is the correct explanation (A).